I have been using screened bottom boards for about 10-15 years.   However, 
I  have noticed that the bees make their brood nest further up in  the brood
chamber.  
I am suspecting that the % of mites that fall thru the screen is a smaller %
than that are chewed by the bees.
 


 
 
 
 
Exactly what I have seen.  Switched back 2 years ago.

Charles 
 
 

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